Gas Laws

Gases No definite shape, no definite volume

Properties of Gases Pressure Pressure is defined as the force the gas exerts on a given area of the container in which it is contained Units- – mm Hg (manometers of mercury) – atm (atmospheres)- air pressure at earth’s sea level – Pa (Pascal) N/m 2

Temperature Measures the kinetic energy of particles Units- – Kelvin (K) – Celsius (C)

Volume Volume is the three-dimensional space inside the container holding the gas. Units- – m 3 – L

Boyle’s Law This law is named for Charles Boyle, who studied the relationship between pressure, p, and volume, V, in the mid-1600s. Boyle determined that for the same amount of a gas at constant temperature, p * V = constant This defines an inverse relationship: when one goes up, the other comes down. pressure volume

Application of Boyle’s Law p 1 * V 1 = p 2 * V 2 p 1 = initial pressure V 1 = initial volume p 2 = final pressure V 2 = final volume With constant temperature and amount of gas, you can use these relationships to predict changes in pressure and volume.

Charles’ Law This law is named for Jacques Charles, who studied the relationship volume, V, and temperature, T, around the turn of the 19 th century. He determined that for the same amount of a gas at constant pressure, V / T = constant This defines a direct relationship: an increase in one results in an increase in the other. volume temperature

Application of Charles’ Law V 1 / T 1 = V 2 / T 2 V 1 = initial volume T 1 = initial temperature V 2 = final volume T 2 = final temperature With constant pressure and amount of gas, you can use these relationships to predict changes in temperature and volume NEXTPREVIOUS MAIN MENU

Lussac’s Law If a gas's temperature increases then so does its pressure, if the mass and volume of the gas are held constant P/T = constant Direct relationship P 1 /T 1 = P 2 / T 2

Combined Gas Law P 1 V 1 / T 1 = P 2 V 2 / T 2 P 1 = initial pressure V 1 = initial volume T 1 = initial temperature P 2 = final pressure V 2 = final volume T 2 = final temperature

IDEAL GAS LAW PV = nRT, where P is pressure (atm or mmHg) V is volume (m 3 or Liters) n is number of moles R is the ideal gas constant = ( atm x L/Mol x K) T is temperature (K) n = m/M, where m is sample mass and M is molar mass